Passionate, as far as I am concerned, means their interaction is intense. This could mean in a non romantic or romantic manner. Basically, if someone is passionate you will likely feel a greater connection mentally or emotionally during the experience as opposed to someone who is disconnected and void of intensity.
Dominant, means being in control BUT it does not indicate S&M exclusively. A lot of dominant partners don't understand that communication and trust needs to be established in some aspect before asserting your dominance. Don't be fooled into someone saying they are dominant but don't treat you good or please you.